What worked for me was that i docked at wilhelmshafen.
I was at the start same as you are now on the second chapter of the campaign.
After i docked at wilhelmshafen i was transferred to lorient.
About the sub i got my new one during the first part of the campaign.
Don`t not what the trigger is to get a new one, i think renown or so an so much sunk tonnage.
My guess is you will get the new one soon.
Perhaps even after your have docked at wilhemhafen
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